Differentials are used to compensate for differences in distances traveled by vehicle wheels, allowing power to be applied to each of a pair of wheels although each wheel travels a different distance, in cornering, for example. Numerous differentials are known. For the most part known differentials have comprised axle gears splined to the wheels axles, a differential case, differential pinion gears on a differential pinion shaft supported by the case, the pinion gears being meshed with the axle gears. A drive pinion driven by the engine drives a ring gear fixed to the case. This effects rotation of the differential case, the differential pinion shaft and differential pinion gears around with the ring gear. If the vehicle is being run down a straight road, the differential turns as a unit with the ring gear without relative movement between components. The differential pinion gears do not rotate on the pinion shaft. Equal torque is applied to the axle gears so that both driven wheels rotate at the same speed. Around a corner, however, the outer wheel must travel farther than the inner wheel in a given period of time and thus must turn faster than the inner wheel. Now the two differential pinion gears rotate on the pinion shaft, so that the outer wheel may turn more rapidly than the inner. On an opposite direction turn, the pinion gears rotate in the opposite direction, to the same effect.
Characteristically, the usual differential is a massive affair with the case and gears made of substantial pieces of heavy metal, contributing unduly to the weight and power requirements of vehicles, and foreclosing modest applications such as golf carts and wheel chairs from efficient differentials.
A different type of differential is disclosed in U.S. Pat. No. 3,919,899 to Parker. In this patent, a differential is described comprising a pair of axle gears affixed to tubular axles, a planetary gear, a central axle passing through the tubular axles to align the unit, and a ring gear connected to the planetary gear and rotatably mounted around the central shaft. While lightweight and effective, this differential still employs a form of pinion gear, the planetary gear, and thus still has weight which is desirably lessened.
Belt and gear devices have been shown in U.S. Pat. No. 0,436,970 to Edison, and in U.S. Pat. No. 3,543,608 to Mehiak, where a smooth belt was wrapped about smooth gears with no means of guiding the belt against wear. In Brit. App. No. 2 058 965, published 15 Apr. 1981 to Gauvain, separate belts are shown engaged with toothed gears in a widely spaced arrangement that does not allow compactness.